Recent developments in anti tumor therapy include the use of autologous bone marrow or peripheral blood stem cell transplantation. Patients subjected to malignant cancers are often treated by lethal chemotherapy and radiotherapy followed by reinfusion of autologous peripheral blood or bone marrow collected prior to the lethal therapy. The decision to make autologous peripheral blood or bone marrow transplantation the treatment of choice for a given cancer depends upon the type of cancer itself and the degree of disease at the time of diagnosis. There is consensus that the autologous transplantation should be performed as soon as the disease is diagnosed and it is desirable to remove tumor cells, or other undesirable populations of cells, from the cells, tissues or fluids that are intended for autologous transplantation prior to infusion or implantation.
Diagnosis can be performed for tumors of the lymphohematopoietic system by molecular means since a number of them are characterized by a genetic disorder that can be determined through use of specific primers and either fluorescent in situ hybridization (FISH) or polymerase chain reaction (PCR) followed by the use of specific probes. Solid tumors on the other hand may require detection at the cellular level using antibodies directed to tumor associated antigens or to tumor markers which occur in sites where the tumor cells are not normally not found (e.g. epithelial specific cytokeratins in the peripheral blood). In the latter case the detection is based on an immunohistochemical stain and a microscopic analysis of the cells. Both molecular and cellular detection mechanisms are dependent on the number of tumor cells in the cell sample. State of the art detection by PCR has sensitivity level of 1/10.sup.5 cells. This implies that by using specific primers, 1 cell in 10.sup.5 non-tumorous cells can be detected with cellular detection being 1/10.sup.5 to 1/10.sup.6 cells. In other words, contaminating solid tumor cells can be detected provided they represent between 0.001 and 0.0001% of the cell mixture. Given the limits of diagnostic detection of tumor cells, in addition to the low number of tumor cells that exist in circulating body fluids, current diagnostic procedures present a high probability of false negative diagnosis of solid tumors.
Among women, breast cancer is by far the leading cause of cancer, with invasive breast cancer affecting approximately one woman in nine. (Lippman, M. E., 1993, Science 259:631-632). The use of fine needle aspiration cytology or excisional biopsy under local anesthesia allows for outpatient diagnosis of breast cancer. Such diagnosis is usually performed in cases where a lump is found in the breast tissue either through routine physical examination, or by mammography, and/or where there is a family history of breast cancer (Cecil Textbook of Medicine, 19th ed., 1992, ed. Wyngaarden et al., pub. W. B. Saunders Co., pp.1381-1386). Since both fine needle aspiration and excisional biopsy procedures are invasive and expose the patient to a certain amount of risk, non-invasive approaches to the diagnosis of breast cancer are preferred.
It is established that breast tumor cells and tumor emboli spread directly to the bloodstream providing an alternative and desirable source of breast tumor cells for diagnostic purposes (Cecil Textbook of Medicine, supra). However, in order to successfully utilize circulating bodily fluids for breast cancer diagnosis, the small number of circulating breast tumor cells must first be enriched, and one must employ highly sensitive and specific techniques to detect the breast tumor cells.
At present, there is a need for a rapid and reproducible procedure suitable for processing a large volume of whole blood which produces high-yield, specific enrichment of breast tumor cells from circulating bodily fluids.